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Author Topic: USB to Serial Adapters  (Read 99810 times)

Charles Johnson

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USB to Serial Adapters
« on: December 03, 2004, 02:32:02 pm »

Greetings all,

I'm upgrading to a new laptop that does not have a serial port on it and am looking for a good USB-to-Serial-Port adapter. Since my main use for it will be to interface with Ashly digital products, I gave Ashly a call to see what they recommended. They (well, to be specific, Mike in the Tech Support Dept) recommended the GUC232A from IOGear. My concern, though, is that this is a USB 1.1 to serial adapter and the USB connections on my new computer (a Thinkpad T42p, for those interested) are USB 2.0. Since I didn't discover the fact that Mike's recommended adapter was a USB 1.1-based adapter until after I hung up w/ him, I didn't get a chance to ask him about it on the phone Confused Technically, my 2.0-based USB connections should be able to handle 1.1-based peripherals, but theory and reality aren't always the same...

Anyhow, I'll be using the serial port to control Ashly digital units  via the Ashly Protea Control software as well as via Smaart. Naturally, I'd like to be able to interface with other RS-232-interface products as well Wink So, with that in mind, what are you using and how well is it working out?

I appreciate your thoughts/comments/suggestions! Cheers!

Charles Johnson

PS Mike - just for the record, I'm not faulting you at all for your recommendation! I was the one who goofed and didn't discover the 1.1 vs 2.0 protocol issue until it was too late.
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Geri O'Neil

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Re: USB to Serial Adapters
« Reply #1 on: December 03, 2004, 07:02:16 pm »

Hey, Charles. I gotta do this quick as I'm running out the door to a show, but I'm using a PC-Card-to-2-serial-port adapter cable. I went through 2 USB-to-serial units and didn't like either one of them. They worked irratically and they consisted of a box that you had to power up (with a wall-wart, naturally), connect to the notebook with a USB cable, then connect to the serial device with a third cable. What a trainwreck! This PC card thing goes, naturally, in the PC card slot of the notebook and breaks out into two serial cables. One set of cables coming from the computer. No power requirements. And the notebook sets up the two serial ports as extra COM ports. I'm controlling an EAW MX-8750 and a set of Ashly Protea EQs at the same time and never an issue to deal with. They also make a unit that breaks out into 4 serial ports. I didn't that many at the time, but the day ain't over... Very Happy
I'll e-mail you some more info when I get in tonight. Sorry, I didn't get the pics of the Protea remote cover you asked about, the thing went out yesterday with the respective rack and won't be in until Monday. YIKES!! GOTTA FLY LIKE THE ODIFEROUS STRIPED WIND THAT WE'RE FAMOUS FOR AROUND HERE!!

More later, Geri O
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Sebastiaan Meijer

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Re: USB to Serial Adapters
« Reply #2 on: December 03, 2004, 07:24:47 pm »

Charles,

Never had an USB 1.1-device fail on an USB 2.0 port. But hey, this is mission critical.
For my powerbook I recently acquired a Keyspan USB 28 adapter, a unit that exists for PC too. Works flawless. Before putting it at work I'm bench testing the alive time and such and it has been online via VirtualPC 7 to the Soundweb for more than 24 hours.

Now if MacFOH comes to the package Smile Wet dreams......

Sebas
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Shanne Flemming

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Re: USB to Serial Adapters
« Reply #3 on: December 03, 2004, 08:48:31 pm »

I use keyspan as well, never had a problem. If you have several USB ports, you will need to find the com port / USB port your hardware is looking for.

Shane
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Juan Turro

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Re: USB to Serial Adapters
« Reply #4 on: December 03, 2004, 10:43:05 pm »

I regularly use the IOgear adapter you mentioned without any trouble and have done so for a few years.  My current laptop has USB 2.0 ports and that does not present any problems.  I have used the IOGear with Soundweb among other audio units.  There was one unit I tried a while back that did not work but it was something I have not used again since so it was unimportant.  The IOgear is USB powered and not in a box.  It is very compact and the electronics are built into the DB-9 connector.  That is why I like it.  It is also sold by Aten who I believe is the manufacturer.  IOgear only resells it under their name.  I hear occasionally about some people who experience issues with USB/RS232 adapters with certain pieces of equipment. Usually it is an older piece of equipment or something not that mainstream.  The PCMCIA to serial port solutions Geri O mentions are usually more compatible with most devices in my experience.  I believe the reason is that the card holds actual UART serial hardware vs. the virtual serial port of the USB adapter.  I have an old IBM PCMCIA adapter I bought years ago that worked well on a lot of equipment.  I think the reason I don't use it much is that I don't like to leave the PCMCIA card in my laptop.  The cable was too long and harder to store in my ultra compact laptop bag.  I already need to take a null modem cable with me.  I also did not like the tiny connection the cable uses to connect to the PCMCIA card.  I realize there are not all the way.  The better PCMCIA/serial adapters I have seen are from Socket and there was one other I cannot recall at the moment, I think it may be Quatech.  There are some Socket units on Ebay at the moment.  I hope this makes sense as I too am in a hurry and wrote this up quickly.  I hope that helps.

Juan
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Andy Peters

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Re: USB to Serial Adapters
« Reply #5 on: December 04, 2004, 03:31:51 pm »

Charles Johnson wrote on Fri, 03 December 2004 12:32

They (well, to be specific, Mike in the Tech Support Dept) recommended the GUC232A from IOGear. My concern, though, is that this is a USB 1.1 to serial adapter and the USB connections on my new computer (a Thinkpad T42p, for those interested) are USB 2.0. Since I didn't discover the fact that Mike's recommended adapter was a USB 1.1-based adapter until after I hung up w/ him, I didn't get a chance to ask him about it on the phone Confused Technically, my 2.0-based USB connections should be able to handle 1.1-based peripherals, but theory and reality aren't always the same...


Time to don the USB-guy hat:

USB 2.0 is backwards-compatible with USB 1.1.  The main difference between the two specs in terms of devices is that 2.0 supports high-speed transfers (480 Mbps), in addition to the two older speeds (full speed or 12 Mbps and low speed, 1.5 Mbps).  The serial gizmo you mention is a full-speed device (probably based on the ubiquitous FTDI chips) and your USB 2.0 host controller in your laptop should have no problems with it.  If there ARE problems, then the device is broken.

RS-232 ports present an interesting problem.  The transmit and receive lines are independent.  Some PC applications will do things like send a command and then expect some sort of response.  RS-232 will allow the response to be almost immediate, although the application may have a timeout, which means that if it doesn't get a response from the device in a certain amount of time, it aborts whatever it was doing and may even think that the device isn't connected.

USB, on the other hand, forces the commands and responses into "packets," and the packets are sent at regular intervals.  If that interval between responses is "too short," then you end up wasting bandwidth because the host (the PC) is always asking the device "do you have anything for me?" and most of the time the answer is no.  If the interval is "too long," then the application may time out because it didn't get a response in time.

Since USB 2.0 is the latest/greatest version of the spec, it's probably impossible to buy a new PC that has USB 1.1 ports.

Another point: you'll probably see lots of devices that are advertised as USB 2.0.  Don't assume that they are high-speed devices unless the packaging explicitly says so.

-a
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Josh Evans

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Re: USB to Serial Adapters
« Reply #6 on: December 09, 2004, 09:20:05 am »


Why not just go wireless?


http://www.extron.com/product/product.asp?id=iplts2
http://www.lantronix.com/device-networking/external-device-s ervers/wibox
.html
http://www.lantronix.com/device-networking/external-device-s ervers/secur
ebox-sds1100.html

www.otcwireless.com

This was discussed on www.synaudcon.com list serve a couple of days ago.

Also iv used the cheap Radio Shack interface with some success.

cheers,
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Joshua Evans

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Charles Johnson

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Re: USB to Serial Adapters
« Reply #7 on: December 09, 2004, 11:41:14 pm »

Andy Peters wrote on Sat, 04 December 2004 15:31

Charles Johnson wrote on Fri, 03 December 2004 12:32

They...recommended the GUC232A from IOGear.


Time to don the USB-guy hat...



Andy,

Since I may need more than 1 serial port at the same time, might something like this from Keyspan be a good idea? Or should I just buy a USB hub and multiple single-serial-port adapters like the IOGear unit?

FYI, it's looking like I'll be using the USBPre for Smaart, so that will take up 1 of my laptop's 2 USB ports. For some shows, the only other USB-based connection I'll need will be to tie in to my Yamaha 01V96. However, for other shows, I'll need at least 1 or more serial ports (to control digital EQs and system processors). For the latter shows, I may or may not be using my digital console, so I won't always need the digital console connection.

Thus, I'm thinking that perhaps the Keyspan device would cover my serial needs and when I need to connect to more than 2 USB devices, I'll use a small USB hub. How does that sound to you? What (if any) potential problems might I encounter with such a setup?

I greatly appreciate the info! Cheers!

Charles Johnson
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Andy Peters

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Re: USB to Serial Adapters
« Reply #8 on: December 10, 2004, 12:07:26 am »

Charles Johnson wrote on Thu, 09 December 2004 21:41

Since I may need more than 1 serial port at the same time, might something like this from Keyspan be a good idea? Or should I just buy a USB hub and multiple single-serial-port adapters like the IOGear unit?


It's probably got a hub already built in.  I took a different one of those four-porters apart, and it had a hub chip and attached to the four downstream hub ports (inside, no external connections, it's all on the PCB) were four of the FTDI232 USB-to-RS232 chips.

When you first plug it in, it'll enumerate the hub, then it will enumerate each of the four USB-to-RS232 chips in turn.  It's stupid, because if you plug it into a different port on your computer it'll re-do the whole thing the first time.  Stupid Windows.

Quote:

Thus, I'm thinking that perhaps the Keyspan device would cover my serial needs and when I need to connect to more than 2 USB devices, I'll use a small USB hub. How does that sound to you? What (if any) potential problems might I encounter with such a setup?


I would make sure to dedicate a port on the laptop for the USBPre and use another port for the serial thing or a hub.  You're also going to have a tangle of DC wires for all of those things!

-a
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Charles Johnson

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Re: USB to Serial Adapters
« Reply #9 on: December 10, 2004, 07:25:11 am »

Andy Peters wrote on Fri, 10 December 2004 00:07


Quote:

Thus, I'm thinking that perhaps the Keyspan device would cover my serial needs and when I need to connect to more than 2 USB devices, I'll use a small USB hub. How does that sound to you? What (if any) potential problems might I encounter with such a setup?


I would make sure to dedicate a port on the laptop for the USBPre and use another port for the serial thing or a hub.  You're also going to have a tangle of DC wires for all of those things!



Andy,

Actually, since both the USBPre and the Keyspan units are USB-powered, I won't have any wall-warts to deal with Very Happy (well, I'll have the line-lump for my laptop, but that's already a given)

Charles Johnson
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Gian P. Portanova

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Re: USB to Serial Adapters
« Reply #10 on: December 10, 2004, 01:50:27 pm »

Anybody sending USB up or down a snake between FOH and stage?
How?
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Andy Peters

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Re: USB to Serial Adapters
« Reply #11 on: December 10, 2004, 02:21:26 pm »

Gian wrote on Fri, 10 December 2004 11:50

Anybody sending USB up or down a snake between FOH and stage?
How?


NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO.  Can't be done.

Some reasons, all relating to the USB spec:

1) First and foremost, the USB spec has a distance limit given as a cable delay of 26 ns, which ends up being 5 meters.  If this cable length is exceeded, you will see packets colliding or bus contention as the drivers on both sides of the bus are enabled at the same time.

2) USB cables are specified to be a tight 90-ohm differential impedance; audio snake impedances are rarely specified at all.  The impedance spec helps ensure good signal integrity.  Remember that the bandwidth full-speed USB at 12 Mbps exceeds that of baseband video, and you don't send video down a snake, right?

3) USB also sends power down the cable so you'd need four wires in your snake line.  The spec also details acceptable voltage drops in the cable; a long audio snake may have significant voltage drop and so VBUS may be out of spec at the far end.

There are various gizmos that purport to translate USB to "something else" (Wireless, CAT-5 cable, whatever) but those devices may have severe limitations.  For example, the so-called "Wireless USB" is good for only low-speed devices (keyboards, mice, that sort of thing).  And the USB-over-CAT5 things use specialized transceivers and depend on high-quality cable, which is why CAT5 is specified.  You don't send Ethernet down a snake, right?

--a
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KeithBroughton

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Re: USB to Serial Adapters
« Reply #12 on: December 19, 2004, 02:16:44 pm »

The GUC232A is just fine.
Works so well, I bought 2.
As far as running USB along a snake...no way!
Try setting up the wireless serial  Bluetooth system as indicated on this link...works GREAT!
http://www.driverack.com/drug/view_thread.asp?forumid=12& ;thread_id=38790
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DanLynch

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Re: USB to Serial Adapters
« Reply #13 on: January 08, 2005, 12:00:11 pm »

We deal with this literally every day.  No matter what anyone tells you, there is NO SUCH THING as "the right" USB to serial adaptor.

Adapter A will work great with a Soundweb but not with an Extron switcher.  Then on a different computer, it won't work with either.  Adapter B will work perfectly with every product as long as you don't have an IBM laptop.  Adapter C will be fantastic on the IBM as well as a Toshiba and a Dell, but it will fall on its face as soon as you use an HP laptop.

If you're getting ready to try USB to serial, do one of two things.

1: Forget it!  Order an ethernet-to-serial adaptor from Moxa.com

2: In the real world of limited budgets, go to the local CircuitCity/CompUSA/whatever and buy one of each brand they have available.  After you figure out which one works for your combination of laptop/gear, return the rest.

If anyone tells you that the Blahblahwoof XL254 is the perfect USB-serial adapter, they're more likely to be wrong than right unless you're both using the exact same laptop with the exact same gear.  Buy a bunch of adaptors and try them all until you find the one that works for you.

Dan
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Re: USB to Serial Adapters
« Reply #13 on: January 08, 2005, 12:00:11 pm »


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